<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>清除浮动的本质以及额外标签法</title>
</head>
    <!-- 清除浮动的本质就是清除浮动元素照成的影响 
    -->
    <style>
        
        .box{
            width: 900px;
            height: 300px;
            background-color: rebeccapurple;
        }
        .daomao{
            width: 200px;
            height: 200px;
            background-color: blue;
        }
        .ermao{
            
            width: 200px;
            height: 150px;
            background-color: red;
        }
        .sanmao{
            width: 300px;
            height: 240px;
            background-color: blue;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="damao">大毛</div>
        <div class="ermao">二毛</div>
       
    </div>
    <div class="sanmao"></div>
</body>
</html>